
  var hardLimit = 100,
    ellipsis = "\u2026",
    DOM = {
      tag: function (tagName, className) {
        var t = document.createElement(tagName);
        t.className = className;
        return t;
      },
      text: function (str) {
        return document.createTextNode(str);
      }
    };
  
  function Stream(enc, pos) {
    if (enc instanceof Stream) {
      this.enc = enc.enc;
      this.pos = enc.pos;
    } else {
      this.enc = enc;
      this.pos = pos;
    }
  }
  Stream.prototype.get = function (pos) {
    if (pos === undefined)
      pos = this.pos++;
    if (pos >= this.enc.length)
      throw 'Requesting byte offset ' + pos + ' on a stream of length ' + this.enc.length;
    return this.enc[pos];
  };
  Stream.prototype.hexDigits = "0123456789ABCDEF";
  Stream.prototype.hexByte = function (b) {
    return this.hexDigits.charAt((b >> 4) & 0xF) + this.hexDigits.charAt(b & 0xF);
  };
  Stream.prototype.hexDump = function (start, end, raw) {
    var s = "";
    for (var i = start; i < end; ++i) {
      s += this.hexByte(this.get(i));
      if (raw !== true)
        switch (i & 0xF) {
          case 0x7: s += "  "; break;
          case 0xF: s += "\n"; break;
          default:  s += " ";
        }
    }
    return s;
  };
  Stream.prototype.parseStringISO = function (start, end) {
    var s = "";
    for (var i = start; i < end; ++i)
      s += String.fromCharCode(this.get(i));
    return s;
  };
  Stream.prototype.parseStringUTF = function (start, end) {
    var s = "";
    for (var i = start; i < end; ) {
      var c = this.get(i++);
      if (c < 128)
        s += String.fromCharCode(c);
      else if ((c > 191) && (c < 224))
        s += String.fromCharCode(((c & 0x1F) << 6) | (this.get(i++) & 0x3F));
      else
        s += String.fromCharCode(((c & 0x0F) << 12) | ((this.get(i++) & 0x3F) << 6) | (this.get(i++) & 0x3F));
    }
    return s;
  };
  Stream.prototype.parseStringBMP = function (start, end) {
    var str = ""
    for (var i = start; i < end; i += 2) {
      var high_byte = this.get(i);
      var low_byte = this.get(i + 1);
      str += String.fromCharCode( (high_byte << 8) + low_byte );
    }
    
    return str;
  };
  Stream.prototype.reTime = /^((?:1[89]|2\d)?\d\d)(0[1-9]|1[0-2])(0[1-9]|[12]\d|3[01])([01]\d|2[0-3])(?:([0-5]\d)(?:([0-5]\d)(?:[.,](\d{1,3}))?)?)?(Z|[-+](?:[0]\d|1[0-2])([0-5]\d)?)?$/;
  Stream.prototype.parseTime = function (start, end) {
    var s = this.parseStringISO(start, end),
      m = this.reTime.exec(s);
    if (!m)
      return "Unrecognized time: " + s;
    s = m[1] + "-" + m[2] + "-" + m[3] + " " + m[4];
    if (m[5]) {
      s += ":" + m[5];
      if (m[6]) {
        s += ":" + m[6];
        if (m[7])
          s += "." + m[7];
      }
    }
    if (m[8]) {
      s += " UTC";
      if (m[8] != 'Z') {
        s += m[8];
        if (m[9])
          s += ":" + m[9];
      }
    }
    return s;
  };
  Stream.prototype.parseInteger = function (start, end) {
    //TODO support negative numbers
    var len = end - start;
    if (len > 4) {
      len <<= 3;
      var s = this.get(start);
      if (s === 0)
        len -= 8;
      else
        while (s < 128) {
          s <<= 1;
          --len;
        }
      return "(" + len + " bit)";
    }
    var n = 0;
    for (var i = start; i < end; ++i)
      n = (n << 8) | this.get(i);
    return n;
  };
  Stream.prototype.parseBitString = function (start, end) {
    var unusedBit = this.get(start),
      lenBit = ((end - start - 1) << 3) - unusedBit,
      s = "(" + lenBit + " bit)";
    if (lenBit <= 20) {
      var skip = unusedBit;
      s += " ";
      for (var i = end - 1; i > start; --i) {
        var b = this.get(i);
        for (var j = skip; j < 8; ++j)
          s += (b >> j) & 1 ? "1" : "0";
        skip = 0;
      }
    }
    return s;
  };
  Stream.prototype.parseOctetString = function (start, end) {
    var len = end - start,
      s = "(" + len + " byte) ";
    if (len > hardLimit)
      end = start + hardLimit;
    for (var i = start; i < end; ++i)
      s += this.hexByte(this.get(i)); //TODO: also try Latin1?
    if (len > hardLimit)
      s += ellipsis;
    return s;
  };
  Stream.prototype.parseOID = function (start, end) {
    var s = '',
      n = 0,
      bits = 0;
    for (var i = start; i < end; ++i) {
      var v = this.get(i);
      n = (n << 7) | (v & 0x7F);
      bits += 7;
      if (!(v & 0x80)) { // finished
        if (s === '') {
          var m = n < 80 ? n < 40 ? 0 : 1 : 2;
          s = m + "." + (n - m * 40);
        } else
          s += "." + ((bits >= 31) ? "bigint" : n);
        n = bits = 0;
      }
    }
    return s;
  };
  
  function ASN1(stream, header, length, tag, sub) {
    this.stream = stream;
    this.header = header;
    this.length = length;
    this.tag = tag;
    this.sub = sub;
  }
  ASN1.prototype.typeName = function () {
    if (this.tag === undefined)
      return "unknown";
    var tagClass = this.tag >> 6,
      tagConstructed = (this.tag >> 5) & 1,
      tagNumber = this.tag & 0x1F;
    switch (tagClass) {
      case 0: // universal
        switch (tagNumber) {
          case 0x00: return "EOC";
          case 0x01: return "BOOLEAN";
          case 0x02: return "INTEGER";
          case 0x03: return "BIT_STRING";
          case 0x04: return "OCTET_STRING";
          case 0x05: return "NULL";
          case 0x06: return "OBJECT_IDENTIFIER";
          case 0x07: return "ObjectDescriptor";
          case 0x08: return "EXTERNAL";
          case 0x09: return "REAL";
          case 0x0A: return "ENUMERATED";
          case 0x0B: return "EMBEDDED_PDV";
          case 0x0C: return "UTF8String";
          case 0x10: return "SEQUENCE";
          case 0x11: return "SET";
          case 0x12: return "NumericString";
          case 0x13: return "PrintableString"; // ASCII subset
          case 0x14: return "TeletexString"; // aka T61String
          case 0x15: return "VideotexString";
          case 0x16: return "IA5String"; // ASCII
          case 0x17: return "UTCTime";
          case 0x18: return "GeneralizedTime";
          case 0x19: return "GraphicString";
          case 0x1A: return "VisibleString"; // ASCII subset
          case 0x1B: return "GeneralString";
          case 0x1C: return "UniversalString";
          case 0x1E: return "BMPString";
          default:   return "Universal_" + tagNumber.toString(16);
        }
      case 1: return "Application_" + tagNumber.toString(16);
      case 2: return "[" + tagNumber + "]"; // Context
      case 3: return "Private_" + tagNumber.toString(16);
    }
  };
  ASN1.prototype.reSeemsASCII = /^[ -~]+$/;
  ASN1.prototype.content = function () {
    if (this.tag === undefined)
      return null;
    var tagClass = this.tag >> 6,
      tagNumber = this.tag & 0x1F,
      content = this.posContent(),
      len = Math.abs(this.length);
    if (tagClass !== 0) { // universal
      if (this.sub !== null)
        return "(" + this.sub.length + " elem)";
      //TODO: TRY TO PARSE ASCII STRING
      var s = this.stream.parseStringISO(content, content + Math.min(len, hardLimit));
      if (this.reSeemsASCII.test(s))
        return s.substring(0, 2 * hardLimit) + ((s.length > 2 * hardLimit) ? ellipsis : "");
      else
        return this.stream.parseOctetString(content, content + len);
    }
    switch (tagNumber) {
      case 0x01: // BOOLEAN
        return (this.stream.get(content) === 0) ? "false" : "true";
      case 0x02: // INTEGER
        return this.stream.parseInteger(content, content + len);
      case 0x03: // BIT_STRING
        return this.sub ? "(" + this.sub.length + " elem)" :
          this.stream.parseBitString(content, content + len);
      case 0x04: // OCTET_STRING
        return this.sub ? "(" + this.sub.length + " elem)" :
          this.stream.parseOctetString(content, content + len);
      //case 0x05: // NULL
      case 0x06: // OBJECT_IDENTIFIER
        return this.stream.parseOID(content, content + len);
      //case 0x07: // ObjectDescriptor
      //case 0x08: // EXTERNAL
      //case 0x09: // REAL
      //case 0x0A: // ENUMERATED
      //case 0x0B: // EMBEDDED_PDV
      case 0x10: // SEQUENCE
      case 0x11: // SET
        return "(" + this.sub.length + " elem)";
      case 0x0C: // UTF8String
        return this.stream.parseStringUTF(content, content + len);
      case 0x12: // NumericString
      case 0x13: // PrintableString
      case 0x14: // TeletexString
      case 0x15: // VideotexString
      case 0x16: // IA5String
      //case 0x19: // GraphicString
      case 0x1A: // VisibleString
        //case 0x1B: // GeneralString
        //case 0x1C: // UniversalString
        return this.stream.parseStringISO(content, content + len);
      case 0x1E: // BMPString
        return this.stream.parseStringBMP(content, content + len);
      case 0x17: // UTCTime
      case 0x18: // GeneralizedTime
        return this.stream.parseTime(content, content + len);
    }
    return null;
  };
  ASN1.prototype.toString = function () {
    return this.typeName() + "@" + this.stream.pos + "[header:" + this.header + ",length:" + this.length + ",sub:" + ((this.sub === null) ? 'null' : this.sub.length) + "]";
  };
  ASN1.prototype.print = function (indent) {
    if (indent === undefined) indent = '';
    document.writeln(indent + this);
    if (this.sub !== null) {
      indent += '  ';
      for (var i = 0, max = this.sub.length; i < max; ++i)
        this.sub[i].print(indent);
    }
  };
  ASN1.prototype.toPrettyString = function (indent) {
    if (indent === undefined) indent = '';
    var s = indent + this.typeName() + " @" + this.stream.pos;
    if (this.length >= 0)
      s += "+";
    s += this.length;
    if (this.tag & 0x20)
      s += " (constructed)";
    else if (((this.tag == 0x03) || (this.tag == 0x04)) && (this.sub !== null))
      s += " (encapsulates)";
    s += "\n";
    if (this.sub !== null) {
      indent += '  ';
      for (var i = 0, max = this.sub.length; i < max; ++i)
        s += this.sub[i].toPrettyString(indent);
    }
    return s;
  };
  ASN1.prototype.toDOM = function () {
    var node = DOM.tag("div", "node");
    node.asn1 = this;
    var head = DOM.tag("div", "head");
    var s = this.typeName().replace(/_/g, " ");
    head.innerHTML = s;
    var content = this.content();
    if (content !== null) {
      content = String(content).replace(/</g, "&lt;");
      var preview = DOM.tag("span", "preview");
      preview.appendChild(DOM.text(content));
      head.appendChild(preview);
    }
    node.appendChild(head);
    this.node = node;
    this.head = head;
    var value = DOM.tag("div", "value");
    s = "Offset: " + this.stream.pos + "<br/>";
    s += "Length: " + this.header + "+";
    if (this.length >= 0)
      s += this.length;
    else
      s += (-this.length) + " (undefined)";
    if (this.tag & 0x20)
      s += "<br/>(constructed)";
    else if (((this.tag == 0x03) || (this.tag == 0x04)) && (this.sub !== null))
      s += "<br/>(encapsulates)";
    //TODO if (this.tag == 0x03) s += "Unused bits: "
    if (content !== null) {
      s += "<br/>Value:<br/><b>" + content + "</b>";
      if ((typeof oids === 'object') && (this.tag == 0x06)) {
        var oid = oids[content];
        if (oid) {
          if (oid.d) s += "<br/>" + oid.d;
          if (oid.c) s += "<br/>" + oid.c;
          if (oid.w) s += "<br/>(warning!)";
        }
      }
    }
    value.innerHTML = s;
    node.appendChild(value);
    var sub = DOM.tag("div", "sub");
    if (this.sub !== null) {
      for (var i = 0, max = this.sub.length; i < max; ++i)
        sub.appendChild(this.sub[i].toDOM());
    }
    node.appendChild(sub);
    head.onclick = function () {
      node.className = (node.className == "node collapsed") ? "node" : "node collapsed";
    };
    return node;
  };
  ASN1.prototype.posStart = function () {
    return this.stream.pos;
  };
  ASN1.prototype.posContent = function () {
    return this.stream.pos + this.header;
  };
  ASN1.prototype.posEnd = function () {
    return this.stream.pos + this.header + Math.abs(this.length);
  };
  ASN1.prototype.fakeHover = function (current) {
    this.node.className += " hover";
    if (current)
      this.head.className += " hover";
  };
  ASN1.prototype.fakeOut = function (current) {
    var re = / ?hover/;
    this.node.className = this.node.className.replace(re, "");
    if (current)
      this.head.className = this.head.className.replace(re, "");
  };
  ASN1.prototype.toHexDOM_sub = function (node, className, stream, start, end) {
    if (start >= end)
      return;
    var sub = DOM.tag("span", className);
    sub.appendChild(DOM.text(
      stream.hexDump(start, end)));
    node.appendChild(sub);
  };
  ASN1.prototype.toHexDOM = function (root) {
    var node = DOM.tag("span", "hex");
    if (root === undefined) root = node;
    this.head.hexNode = node;
    this.head.onmouseover = function () { this.hexNode.className = "hexCurrent"; };
    this.head.onmouseout  = function () { this.hexNode.className = "hex"; };
    node.asn1 = this;
    node.onmouseover = function () {
      var current = !root.selected;
      if (current) {
        root.selected = this.asn1;
        this.className = "hexCurrent";
      }
      this.asn1.fakeHover(current);
    };
    node.onmouseout  = function () {
      var current = (root.selected == this.asn1);
      this.asn1.fakeOut(current);
      if (current) {
        root.selected = null;
        this.className = "hex";
      }
    };
    this.toHexDOM_sub(node, "tag", this.stream, this.posStart(), this.posStart() + 1);
    this.toHexDOM_sub(node, (this.length >= 0) ? "dlen" : "ulen", this.stream, this.posStart() + 1, this.posContent());
    if (this.sub === null)
      node.appendChild(DOM.text(
        this.stream.hexDump(this.posContent(), this.posEnd())));
    else if (this.sub.length > 0) {
      var first = this.sub[0];
      var last = this.sub[this.sub.length - 1];
      this.toHexDOM_sub(node, "intro", this.stream, this.posContent(), first.posStart());
      for (var i = 0, max = this.sub.length; i < max; ++i)
        node.appendChild(this.sub[i].toHexDOM(root));
      this.toHexDOM_sub(node, "outro", this.stream, last.posEnd(), this.posEnd());
    }
    return node;
  };
  ASN1.prototype.toHexString = function (root) {
    return this.stream.hexDump(this.posStart(), this.posEnd(), true);
  };
  ASN1.decodeLength = function (stream) {
    var buf = stream.get(),
      len = buf & 0x7F;
    if (len == buf)
      return len;
    if (len > 3)
      throw "Length over 24 bits not supported at position " + (stream.pos - 1);
    if (len === 0)
      return -1; // undefined
    buf = 0;
    for (var i = 0; i < len; ++i)
      buf = (buf << 8) | stream.get();
    return buf;
  };
  ASN1.hasContent = function (tag, len, stream) {
    if (tag & 0x20) // constructed
      return true;
    if ((tag < 0x03) || (tag > 0x04))
      return false;
    var p = new Stream(stream);
    if (tag == 0x03) p.get(); // BitString unused bits, must be in [0, 7]
    var subTag = p.get();
    if ((subTag >> 6) & 0x01) // not (universal or context)
      return false;
    try {
      var subLength = ASN1.decodeLength(p);
      return ((p.pos - stream.pos) + subLength == len);
    } catch (exception) {
      return false;
    }
  };
  ASN1.decode = function (stream) {
    if (!(stream instanceof Stream))
      stream = new Stream(stream, 0);
    var streamStart = new Stream(stream),
      tag = stream.get(),
      len = ASN1.decodeLength(stream),
      header = stream.pos - streamStart.pos,
      sub = null;
    if (ASN1.hasContent(tag, len, stream)) {
      // it has content, so we decode it
      var start = stream.pos;
      if (tag == 0x03) stream.get(); // skip BitString unused bits, must be in [0, 7]
      sub = [];
      if (len >= 0) {
        // definite length
        var end = start + len;
        while (stream.pos < end)
          sub[sub.length] = ASN1.decode(stream);
        if (stream.pos != end)
          throw "Content size is not correct for container starting at offset " + start;
      } else {
        // undefined length
        try {
          for (;;) {
            var s = ASN1.decode(stream);
            if (s.tag === 0)
              break;
            sub[sub.length] = s;
          }
          len = start - stream.pos;
        } catch (e) {
          throw "Exception while decoding undefined length content: " + e;
        }
      }
    } else
      stream.pos += len; // skip content
    return new ASN1(streamStart, header, len, tag, sub);
  };
  ASN1.test = function () {
    var test = [
      { value: [0x27],                   expected: 0x27     },
      { value: [0x81, 0xC9],             expected: 0xC9     },
      { value: [0x83, 0xFE, 0xDC, 0xBA], expected: 0xFEDCBA }
    ];
    for (var i = 0, max = test.length; i < max; ++i) {
      var pos = 0,
        stream = new Stream(test[i].value, 0),
        res = ASN1.decodeLength(stream);
      if (res != test[i].expected)
        document.write("In test[" + i + "] expected " + test[i].expected + " got " + res + "\n");
    }
  };

// export globals
  //globals.ASN1 = ASN1;
export  default  ASN1;
